the cause of the present trouble. Another rare cause, resulting in similar symptoms, lay in the loosening of the carbon pole in the cell of a battery. But, just now, the batteries were not at fault.

Finally, as a last resort, Matt examined the gasolene that was being fed into the carburetor. A few drops in the palm of his hand aroused his suspicions. The next moment the hydrometer test was made and water was found in the gasolene.

"How did it get there?" demanded Dick. "The gasolene has worked well enough all afternoon and so far during the night."

"None of the gasolene you bought in Port-of-Spain has been used as yet?"

"Not a drop."

"Well, connect up the carburetor with the storage reservoir. If there is a little water in the carburetor, it will soon work out. After that, empty this tank, strain the gasolene through chamoiskin, and then give the tank a compressed-air treatment. I'll send Clackett to help you."

"But how, in the name of sin, did water get in that tank?" cried the perplexed Dick.

As Matt turned to crawl away, he picked up a six-inch ebony cylinder, about the size of a lead-pencil, from near the tank. It was a chopstick!

"Has the Chinaman been here?" he asked.

"Not that I know of," answered Dick. "Why?"

"Nothing," said Matt, but he was doing some tall thinking as he stepped into the torpedo room, aroused Clackett, and sent him aft to lend Dick a hand.